Anti-reflux esophageal prosthesis or stents are typically placed in the lower esophagus and through the lower esophageal sphincter to maintain the patency thereof due to the presence of a cancerous tumor commonly found in the vicinity thereof. The cancerous tumor growth typically impinges the flow of food and fluids through the esophagus. Lower esophageal cancer in the United States presently occurs at the rate of approximately 12,000 patients per year. The incidence in the United States is approximately 5.1 per 100,000 people, and is rising, particularly in white male patients. Esophageal prosthesis or stents are typically utilized in these cancerous patients. However, these devices are not FDA approved for benign tumors which also cause blockage or partial stenosis of the esophagus. Esophageal prosthesis or stents are utilized in Europe and other countries for benign tumor conditions, but are not being utilized in the United States at this time.
A problem with esophageal prosthesis or stents is that fluid from the stomach flows into the mouth of the patient when in a prone position. In an attempt to solve this problem, a number of esophageal prosthesis or stents utilize a one-way valve such as a duck-bill or reed-type valve in which food or fluid from the esophagus flows into the stomach in only an antegrade or forward direction. However, these one-way anti-reflux prosthesis or stents present certain problems. For example, when the patient wants to belch or vomit, he/she is prevented from doing so because the one-way valve prevents backward flow in the retrograde direction. Such a condition is not only painful to the patient, but can also lead to more complicated medical conditions.
There are other anatomical sites, such as the biliary tree or genitourinary system, in which a prosthesis may be placed to maintain an open lumen for passage of bodily fluids. Such prosthesis may create the risk of undesirable retrograde flow and/or migration of pathogenic organisms, which could lead to infection or other problems, such as obstruction of the stent. When a drainage stent or catheter is placed across a sphincter or natural stricture at the opening to a bodily passage, the sphincter or stricture cannot fulfill its normal function of restricting retrograde flow or migration. What is needed is a prosthesis and one-way valve that can effectively regulate antegrade and retrograde flow in response to the normal flow rates and pressures that exist across the site in which the prosthesis is placed.